This invention relates to the regeneration of activated carbon. More particularly, the invention relates to the regeneration of activated carbon by exothermic reaction of gases and/or vapors passed therethrough.
Activated carbon beds used for purification processes must be periodically regenerated to remove the materials adsorbed thereon. For example, in copending patent application Ser. No. 765,346, filed Feb. 3, 1977 entitled "Disposal of Waste Gases from Production of Aluminum Chloride", assigned to the assignee of this invention, activated carbon beds are shown for the adsorption of various materials emanating from a chlorinator used to chlorinate aluminum oxide. The activated carbon adsorber is particularly useful in that instance for the absorption of other heavy metal chlorides. The activated carbon bed is then regenerated by passing a heated gas such as N.sub.2 or CO.sub.2 therethrough to heat the carbon bed causing the adsorbed materials to be swept out with the purging gas.
Unfortunately, however, such processes require substantial energy to heat the inert sweeping gas such as N.sub.2, CO.sub.2, etc. It would be desirable to provide a means for regenerating the activated carbon bed without the necessity of adding additional heat energy to the process.
It is known to react gases and/or vapors together to exothermically form products in an activated carbon bed. For example, in copending Application Ser. No. 765,281, filed Feb. 3, 1977 and entitled "Waste Gas Treatment System for Chlorine Gas from Production of Aluminum Chloride", and assigned to the assignee of this invention, a process is described for purification of off-gases from a reactor for chlorinating aluminum compounds which comprises passing a mixture of gases containing CO, CO.sub.2, and Cl.sub.2 over activated carbon at a temperature of at least 100.degree. C and for a space time of at least 0.05 minutes to form COC1.sub.2 from the Cl.sub.2 and the CO in the inlet gas. This process is used to remove the chlorine from the chlorinating reactor off-gas. When necessary, additional CO is added to provide the proper stoichiometry for complete reaction of the Cl.sub.2.
It has now been discovered that an activated carbon bed having other materials previously adsorbed thereon may be regenerated without the addition of additional heat energy by passing gases and/or vapors through the activated carbon bed which will react in situ in the bed to release exothermic heat thereby heating the bed to a sufficient temperature to permit removal of the adsorbed materials thereon.